The research project is designed to investigate the role of immunologic mechanisms in the pathogenesis and prevention of experimental corneal allograft rejection. Previous studies have demonstrated that pretreatment of rabbit corneal allografts with either homologous or heterologous antibody against histocompatibility antigens significantly prolongs graft survival. The present proposed work will investigate the attachment sites, duration of attachment, fate of the antibody, and the mechanism involved in prolongation of graft survival. In addition, studies will be carried out on the effects of pretreatment of corneal allografts with antibody combined with topical and/or systemic corticosteroids.